1. Field of the Invention
The invention relates to a failure diagnosis apparatus of a hybrid vehicle.
2. Description of Related Art
Japanese Patent Application Publication No. 2001-231106 (JP-2001-231106 A) discloses a hybrid vehicle capable of external electric power supply. The hybrid vehicle disclosed in JP-2001-231106 A is capable of generating electric power by utilizing an engine output during stop of the vehicle. In addition, the hybrid vehicle disclosed in JP-2001-231106 A is capable of transmitting the generated electric power to the outside of the vehicle.
There is proposed a technique in which a threshold value of SOC of a battery used for determining whether to start or stop an engine during external electric power supply is made different from a threshold value of SOC of the battery while the vehicle is running (see Japanese Patent Application Publication No. 2008-247252 (JP-2008-247252 A)).
In addition, there is also proposed a technique in which, at a time that a system is activated, a failure determination and turning-on of an alarm lamp are performed after a time required for an abnormality determination by an engine electronic control unit (ECU) and a time required for communication with a hybrid ECU elapse (see Japanese Patent Application Publication No. 2009-137453 (JP-2009-137453 A)).
Further, there is also proposed a technique in which a failure determination of an engine is performed based on the state of electric power generation of a motor generator (see Japanese Patent Application Publication No. 2002-047991 (JP-2002-047991 A)).
A vehicle includes a failure diagnosis system. The vehicle has an internal combustion engine mounted thereon. The failure diagnosis system diagnoses the failure of each portion of the internal combustion engine. The failure diagnosis system diagnoses the failure state in a failure diagnosis target based on various diagnosis conditions corresponding to the failure diagnosis targets. However, the failure diagnosis system of a related art is constructed on the assumption of the normal running of the internal combustion engine. Consequently, the failure diagnosis system of the related art does not respond to a change in the use of the internal combustion engine resulting from technological advancement in recent years. The change in the use of the internal combustion engine includes supply of electric power generated by utilizing the power of the internal combustion engine to the outside.
When the internal combustion engine is operated in order to cause a generator to generate electric power, the operation state of the internal combustion engine is different from that during normal running in many cases. For example, the vehicle is stopped during external electric power supply. However, even during the external electric power supply, the load of the internal combustion engine is changed according to the requested amount of the generated electric power. This is because the internal combustion engine is operated in order to drive the generator. Accordingly, if no countermeasure is taken, when the external electric power supply is to be executed in such a hybrid vehicle, there is a possibility that the failure diagnosis system makes an erroneous determination. The erroneous determination is a determination that the internal combustion engine has a failure.
At this point, in a case where any failure is detected, the operation of the internal combustion engine is stopped depending on the location of the failure. Alternatively, measures such as restricting the operation of the internal combustion engine and the like are often taken. Therefore, the failure diagnosis with low accuracy can be a factor that restricts opportunity for the external electric power supply. In addition, in many vehicles, when the failure is detected, a driver is notified of the detection of the failure by turning on a lamp or an indicator. The lamp and the indicator are disposed in an information display or the like in the vehicle. In the vehicle that notifies the driver of the detection of the failure, even when the operation of the internal combustion engine is not stopped or restricted, it is sufficiently conceivable that the driver may stop the internal combustion engine based on his or her decision. With this, the external electric power supply is stopped. In addition, a failure history is often stored in various computer devices that control the vehicle. The storage of the failure detection history based on an inaccurate failure diagnosis is not desirable for the owner of the vehicle.